Pretty sure they changed to a 4-3 when John Fox got there a few years ago.

Their look can be like a 4-3, but basically, their base is more like a 52, same as the Texans. It was explained on the Broncos website by a couple of guys who know the X and O as much as Rey does.

If you follow what Kubiak said about how much we were in the dime and nickel;
the Broncos were, too.
There isn't much difference, just the cirscumstances that prompted the media to classify one from the other.